BrightSource Energy Inc.'s effort to build solar power plants in the Mojave Desert won increased financial support from the federal government on Monday as well as a $168 million investment from Google Inc.

BrightSource, based in Oakland, started construction last fall on a series of three power plants that will use fields of mirrors focused on a central tower to generate electricity, enough for 140,000 homes. The plants, collectively referred to as the Ivanpah Solar Energy Generating System, will sell their electricity to Pacific Gas and Electric Co. and Southern California Edison.

The U.S. Department of Energy last year tentatively awarded the project $1.37 billion in loan guarantees as part of the federal government's economic stimulus program. But the department upped that figure to $1.6 billion on Monday when it finalized terms of the financing.

At the same time, Google chose to make Ivanpah the Internet search company's largest clean-energy investment so far.

"We're excited about Ivanpah because our investment will help deploy a compelling solar energy technology that provides reliable clean energy, with the potential to significantly reduce costs on future projects," Rick Needham, Google's director of green business operations, wrote on the company's official blog.

Last year, power plant operator NRG Energy Inc. agreed to invest $300 million in the Ivanpah project, which will cost roughly $2.2 billion. Ivanpah is expected to be fully operational by mid-2013.